Angiogenesis or neovascularization is critical for normal physiological processes such as embryonic development and wound repair (Folkman and Shing, J. Biol. Chem. 1992, 267:10931-10934; D'Amore and Thompson, Ann. Rev. Physiol. 1987, 49:453-464). However, angiogenesis occurs pathologically, for example, in ocular neovascularization (leading to diabetic retinopathy, neovascular glaucoma, retinal vein occlusion and blindness), in rheumatoid arthritis and in solid tumors (Folkman and Shing, J. Biol. Chem., 1992, 267:10931-10934; Blood and Zetter, Biochim. Biophys. Acta 1990, 1032:118-128).
Tumor dissemination, or metastasis, involves several distinct and complementary components, including the penetration and transversion of tumor cells through basement membranes and the establishment of self-sustaining tumor foci in diverse organ systems. To this end, the development and proliferation of new blood vessels, or angiogenesis, is critical to tumor survival. Without neovascularization, tumor cells lack the nourishment to divide and will not be able to leave the primary tumor site (Folkman and Shing, J. Biol. Chem. 1992, 267:10931-10934).
Inhibition of angiogenesis in animal models of cancer has been shown to result in tumor growth suppression and prevention of metastatic growth (Herblin et al., Exp. Opin. Ther. Patents. 1994, 1-14). Many angiogenic inhibitors have been directed toward blocking initial cytokine-dependent induction of new vessel growth, e.g. antibodies to endothelial cell growth factors. However, these approaches are problematic because tumor and inflammatory cells can secrete multiple activators of angiogenesis (Brooks, et al., Cell 1994, 79:1157-1164). Therefore, a more general approach that would allow inhibition of angiogenesis due to a variety of stimuli would be of benefit.
The integrin .alpha..sub.v .beta..sub.3 is preferentially expressed on angiogenic blood vessels in chick and man (Brooks, et al., Science 1994, 264:569-571; Enenstein and Kramer, J. Invest. Dermatol. 1994, 103:381-386). Integrin .alpha..sub.v .beta..sub.3 is the most promiscuous member of the integrin family, allowing endothelial cells to interact with a wide variety of extracellular matrix components (Hynes, Cell 1992, 69:11-25). These adhesive interactions are considered to be critical for angiogenesis since vascular cells must ultimately be capable of invading virtually all tissues.
While integrin .alpha..sub.v .beta..sub.3 promotes adhesive events important for angiogenesis, this receptor also transmits signals from the extracellular environment to the intracellular compartment (Leavesley, et al., J. Cell Biol. 1993, 121:163-170, 1993). For example, the interaction between the .alpha..sub.v .beta..sub.3 integrin and extracellular matrix components promotes a calcium signal required for cell motility.
During endothelium injury, the basement membrane zones of blood vessels express several adhesive proteins, including but not limited to von Willebrand factor, fibronectin, and fibrin. Additionally, several members of the integrin family of adhesion receptors are expressed on the surface of endothelial, smooth muscle and on other circulating cells. Among these integrins is .alpha..sub.v .beta..sub.3, the endothelial cell, fibroblast, and smooth muscle cell receptor for adhesive proteins including von Willebrand factor, fibrinogen (fibrin), vitronectin, thrombospondin, and osteopontin. These integrins initiate a calcium-dependent signaling pathway that can lead to endothelial cell, smooth muscle cell migration and, therefore, may play a fundamental role in vascular cell biology.
An antibody to the .alpha..sub.v .beta..sub.3 integrin has been developed that inhibits the interaction of this integrin with agonists such as vitronectin (Brooks, et al., Science 1994, 264:569-571). Application of this antibody has been shown to disrupt ongoing angiogenesis on the chick chorioallantoic membrane (CAM), leading to rapid regression of histologically distinct human tumor transplanted onto the CAM (Brooks, et al., Cell 1994, 79:1157-1164). In this model, antagonists of the .alpha..sub.v .beta..sub.3 integrin induced apoptosis of the proliferating angiogenic vascular cells, leaving pre-existing quiescent blood vessels unaffected. Thus, .alpha..sub.v .beta..sub.3 integrin antagonists have been shown to inhibit angiogenesis. Based on this property, therapeutic utility of such agents is expected in human diseases such as cancer, rheumatoid arthritis and ocular vasculopathies (Folkman and Shing, J. Biol. Chem. 1992, 267:10931-10934).
Increasing numbers of other cell surface receptors have been identified which bind to extracellular matrix ligands or other cell adhesion ligands thereby mediating cell-cell and cell-matrix adhesion processes. These receptors belong to a gene superfamily called integrins and are composed of heterodimeric transmembrane glycoproteins containing .alpha.- and .beta.-subunits. Integrin subfamilies contain a common .beta.-subunit combined with different .alpha.-subunits to form adhesion receptors with unique specificity. The genes for eight distinct .beta.-subunits have been cloned and sequenced to date.
Two members of the .beta..sub.1 subfamily, .alpha..sub.4 .beta..sub.1 and .alpha..sub.5 .beta..sub.1 have been implicated in various inflammatory processes. Antibodies to .alpha.4 prevent adhesion of lymphocytes to synovial endothelial cells in vitro, a process which may be of importance in rheumatoid arthritis (VanDinther-Janssen, et al., J. Immunol. 1991, 147:4207). Additional studies with monoclonal anti-.alpha.4antibodies provide evidence that .alpha..sub.4 .beta..sub.1 may additionally have a role in allergy, asthma, and autoimmune disorders (Walsh, et al., J. Immunol. 1991, 146:3419; Bochner, et al., J. Exp. Med. 1991 173:1553; Yednock, et al., Nature 1992, 356:63). Anti-.alpha.4 antibodies also block the migration of leukocytes to the site of inflammation (Issedutz, et al., J. Immunol. 1991, 147:4178).
The .alpha..sub.v .beta..sub.3 heterodimer is a member of the .beta..sub.3 integrin subfamily and has been identified on platelets, endothelial cells, melanoma, smooth muscle cells, and osteoclasts (Horton and Davies, J. Bone Min. Res. 1989, 4:803-808; Davies, et al., J. Cell. Biol. 1989, 109:1817-1826; Horton, Int. J. Exp. Pathol. 1990, 71:741-759). Like GPIIb/IIIa, the vitronectin receptor binds a variety of RGD-containing adhesive proteins such as vitronectin, fibronectin, VWF, fibrinogen, osteopontin, bone sialo protein II and thrombospondin in a manner mediated by the RGD sequence. A key event in bone resorption is the adhesion of osteoclasts to the matrix of bone. Studies with monoclonal antibodies have implicated the .alpha..sub.v .beta..sub.3 receptor in this process and suggest that a selective .alpha..sub.v .beta..sub.3 antagonist would have utility in blocking bone resorption (Horton, et al., J. Bone Miner. Res. 1993, 8:239-247; Helfrich, et al., J. Bone Miner. Res. 1992, 7:335-343)
PCT Patent Application WO 94/22835 discloses compounds having the general formula: EQU (M.sup.1).sub.n --Q--(M.sup.2).sub.1-n --L--A
European Patent Application Publication Number 614664 discloses compounds having the general formula: ##STR1##
PCT Patent Application WO 94/29273 discloses compounds having the general formula: ##STR2##
PCT Patent Application WO 96/18602 discloses compounds having the general formula: ##STR3##
European Patent Application Publication Number EP 635492 discloses compounds having the general formula: ##STR4##
PCT Patent Application WO 96/22288 discloses compounds having the general formula: ##STR5##
None of the above references teaches or suggests the compounds of the present invention which are described in detail below.